I'm in the process of reading this book--but I'm sorry I don't know who Weidler is. I'll try to address the question more like "Is Howard Roark being selfless in chapter 15?"
See, I'm going to be writing an essay about the novel and...well, I hope I can convey my ideas in a way that may be helpful to both of us!
In chapter 15 Keating kills Heyer (well, aids in his death), wins the competiton (by cheating and using Roark's design), and gets rich and famous. What a jerk, right?
Keating and his guilt gives Roark a check for his work on the Cosmo-Slotnick building, but Roark returns it with the condition that Keating never mentions his involvement. Keating is insulted and wants to destroy Roark and his business, though he's broke as it is already.
The one commission that Roark recieves is not "his style" and he refuses, though this potential income could have saved his business. Roark finds Mike, who refers him to a job in the granite quarry.
Roark's "selflessness" could be one point of view towards his refusal of Keating's check and of the commission. It would be so easy to accept the money and the job and get out of his slump but he refuses.
Is it selflessness? Or is it pride? Roark is actually an extremely selfish person...but in a way he sacrifices himself for the sake of retaining his individuality--retaining himself. It's almost a paradox--and depending how you look at it, Roark can be selflessly and self-sacrificially devoted to architecture, or selfishly devoted to his own work, ideas, pride, stature, accomplishments.
I think of it this way--he is giving up one part of himself for the sake of another part. He's giving up the opportunity to make money for the sake of his integrity. He's giving up potential commissions or even fame because he is unwilling to compromise who he is and what he does.
Not knowing Weidler's point of view, I could only assume that externally, Roark refusing Keating's check would be a selfless act. "I don't need your money, I helped you out of the sheer goodness of my heart." But that's not what Roark is really thinking, is he?
I hope this in some remote way helps to answer your question...I'm sorry if I completely circled around it. But thank you for giving me a topic about The Fountainhead! Maybe it was a selfish act of mine to answer this question...!! lol